Many aspects of spatial vision improve significantly during the first year of life At birth, contrast sensitivity, contrast discrimination threshold, grating acuity, and vernier acuity are all at least an order of magnitude poorer than mature values. Two primary goals in studies of visual development are: (a) to determine the consequences of such low sensitivity to the perception of various visual attributes and (b) to understand the optical and neural underpinnings of perinatal deficits and post- natal improvements. This application outlines a program of research to examine several aspects of spatial and chromatic visual sensitivity early in life. The guiding theme for much of the proposed research can be stated as a question: To what extent can age-related changes in pre-neural structures (e.g., optics, and photoreceptors) account for early spatial and chromatic visual deficits and their subsequent improvement? Answers to this question will help delineate the relative contributions of pre- neural and neural development to age changes in visual function. There are four specific aims. (1) We will construct ideal observers with the characteristics of the eyes and photoreceptors of infants of various ages. Their performance will be examined for a variety of spatial and chromatic visual tasks. Disparities in ideal performance at various ages will help delineate the consequences of immature optics and photoreceptors. (2) We will examine several aspects of the development of luminance contrast sensitivity and grating and vernier acuity. The experiments will provide useful data in their own right, but they are particularly important to deducing the consequences of immature photoreception on the development of performance in these tasks. (3) We will examine the development of chromatic sensitivity, too. Again these experiments will provide useful data in their own right, but they are designed specifically to determine if age changes in overall visual efficiency are sufficient to explain the development of chromatic discrimination or whether age changes in chromatic mechanisms per se are implied. (4) Finally, we will study the development of spatial phase discrimination using a paradigm that has illuminated fascinating anomalies in normal adult peripheral vision and in the central vision of adult amblyopes. We will examine the relationship between these phase anomalies and infants' phase sensitivity.